2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/69069We study Pippenger's model of Boolean networks with unreliable gates. In this model, the conditional probability that a particular gate fails, given the failure status of any subset of gates preceding it in the network, is bounded from above by some $ε$. We show that if we pick a Boolean network with $n$ gates at random according to the Barak-Erdős model of a random acyclic digraph, such that the expected edge density is $c n^{-1}\log n$, and if $ε$ is equal to a certain function of the size of the largest reflexive, transitive closure of a vertex (with respect to a particular realization of the random digraph), then Pippenger's model exhibits a phase transition at $c=1$. Namely, with probability $1-o(1)$ as $n\to\infty$, we have the following: for $0 \le c \le 1$, the minimum of the probability that no gate has failed, taken over all probability distributions of gate failures consistent with Pippenger's model, is equal to $o(1)$, whereas for $c >1$ it is equal to $\exp(-\frac{c}{e(c-1)}) + o(1)$. We also indicate how a more refined analysis of Pippenger's model, e.g., for the purpose of estimating probabilities of monotone events, can be carried out using the machinery of stochastic domination.20 pages, 1 eps figure; made some cosmetic changes, corrected a few errorsProbabilityDisordered Systems and Neural NetworksMathematical PhysicsCombinatorics82B26; 94C10; 60K10; 05C20; 05C80text